This invention relates to the separation of articles according to predetermined characteristics, and more particularly to a novel system by which logs and like elongated articles may be sorted accordingly to a wide variety of characteristics and parameters.
Although the system of this invention has wide application to the sorting of diverse types of articles, it has particular utility in the sorting of logs. The sorting of logs to achieve the best and most profitable use for each piece is becoming increasingly important as the raw material becomes most costly and complete utilization becomes more essential. Thus, as the availability of the larger diameter old growth timber decreases, the need to utilize the smaller diameter regrowth and second growth material becomes more essential, in order to satisfy the ever increasing demand for pulp, plywood, timbers, lumber and other forest related products. This places upon the industry the many burdens associated with the handling of many more smaller size logs in order to produce the same volume of wood fiber as was available from old growth logs. It has been estimated that the number of logs required for merely maintaining such volume of wood fiber is increasing about 30% per year.
Utilization of such smaller diameter logs necessarily increases the number of parameters for sorting. For example, the sorting yards of some of the larger mill operations require as many as 52 sorts.
The earlier storage and sorting operations in water ponds is economically unfeasible with the present requirement of handling several times the number of logs. The sorting of logs currently is done primarily by the use of dry deck log sorting yards, utilizing front end loaders with special log handling attachments. These loaders off-load the trucks onto scaling decks, chains, or ground sills, where the logs are graded visually according to species, quality amd classification. The logs then are marked and conveyed by chain or front end loader to a crane shovel type machine where the marked logs are sorted and placed into bins or bunks designated to receive them. From these bins or bunks the logs are picked up by front end loaders and taken to storage decks, or directly to the mill for processing.
The foregoing conventional dry deck log sorting yard designed for the mechanical sorting of logs at sufficiently high rates of speed, are extremely expensive, complex installations requiring a sizeable operating crew and a large support force of machines and operators. Accordingly, they are affordable only by the largest corporations. Even so, they present a very hazardous work area for personnel involved in their operation. Moreover, such sorting yards result in excessive log and fiber damage.